Hello! I am quite new with this forum and have been using NefMoto and KKL cable for short time to read and flash tuned files in my ECU successfully. My car is an Audi A4 B6 1.8t with AVJ engine and has quite a lot miles in it. Lately it has been every now and then throwing an DTC code "P0420 Catalyst System Efficiency Below Threshold". Despite the DTC code it passed emission tests without any problems in inspection so I decided to "save" some money and just to numb rear O2 sensor to get rid of the annoyingly glowing engine light.

I wrote a new file which had some changes on AHKAT values on my ECU and later on realized that it was not apparently properly checksumed. Flashing process succeeded without any errors and I was able to start and run my engine after flashing without any problems. Next morning tried to again start my car, but it did not start. It was only cranking and the radiator fan was blowing like hell. I tried to connect with Nefmoto and VCDS, but either could not make connection.  

After disconnecting the ground from my battery and resetting the ECU I am able to start my engine again. I am also able to now connect with Nefmoto and VCDS when the engine is running, but when I stop the engine I lose the connection and it requires another disconnection of battery if I want to start my engine or to have software connected.

My noob question is now, that are there two different memories in my ECU which I have partly bricked? Can I re-write my ECU while the engine is running as that is the only possibility to have connection to ECU or do I need to invest in Galletto and rewrite with original healthy file in boot mode?

/Juha


                  

What happens if you disconnect the battery and then try and connect, and not start it?

If that doesn't work, bootmode.  It's not as simple a process as just flashing though; it should be known.